French banker, philanthropist and amateur naturalist. Delessert had a passion for collecting and built up a fine library and art collection as well as collections of shells and dried plants. In the mould of Joseph Banks, Delessert collected for the purposes of scientific research, not simply to build up a cabinet of curiosities, and his Paris home became a meeting place for men of science, art and politics. His collections later formed the nucleus of the herbarium at Geneva's Conservatoire botanique.

Jules Paul Benjamin Delessert (known as Benjamin) was born in Lyon but spent most of his youth in Paris, where his father was a banker. The family had strong ties to Switzerland, partly because Delessert's mother was Swiss and because his father's protestant family had moved to the country after the repeal of the edict of Nantes. Delessert's father, Étienne Delessert, no doubt fostered his son's business acumen; he founded the antecedent of the Banque de France and was widely involved in industrialisation and the improvement of agriculture. Benjamin Delessert's botanical interests, meanwhile, were aroused when his mother received Elementary Letters on Botany (1789) from Jean Jacques Rousseau. The text was meant for Delessert's sister, Marguerite, along with a small herbarium, but the young Delessert appropriated both the interest and the collection.

In 1784 he went to Scotland to study at Edinburgh University. In Britain he met luminaries including the economist Adam Smith (1723-1790) and the inventor James Watt (1736-1819). Thus educated, he returned to France and served in the National Guard, deciding to enter into a military career in 1793. He served in campaigns in Belgium and the Netherlands, and while performing as commander of the Antwerp citadel heard the news that his eldest brother, imprisoned by revolutionaries, had died. Delessert returned to Paris to step into his brother's role as head of the family bank, continuing in this directorship for more than half a century. As well as running the bank he established a sugar refinery (1801) and a cotton factory (1803) at Passy, and became a great patron of science. These and other efforts in French commerce during the difficult era of the Napoleonic Wars earned him the Cross of the Legion of Honour and the title Baron of the Empire from Napoleon. He also became a great patron of science and a zealous philanthropist. For example he set up (with his good friend, the botanist Augustin-Pyramus de Candolle) a soup kitchen for the poor of Paris and went on to found charitable institutions such as child-care houses. In 1807 he had married his cousin, Laure Delessert. She died childless in 1823, after which Delessert devoted even more time to his business and philanthropic activities.

It was around the turn of the 19th century that he began to acquire an increasing number of items for his natural history collections. He took advice from A.-P. de Candolle, who stayed in Paris from 1797 to 1811. The pair became lifelong friends, de Candolle becoming well acquainted with members of the Delessert family and often working in Delessert's herbarium. It was no doubt this relationship that later saw the Parisian herbarium deposited in Geneva, de Candolle's home.

Delessert acquired several important herbaria in the early years of the 1800s. In 1803 he added the collection of Luis-Guillaume Lemonnier (1717-1799) to his herbarium, and in 1810 that of Nikolaas Burman (1733-1793), which included plants collected by Thunberg and specimens from Lapland donated by Linnaeus. In 1817 he appointed a paid curator for the collection (Achille Richard, 1794-1852) and in 1830 a librarian, Antoine Lasègue (1793-1873). Antoine Guillemin (1796-1842) was also a member of staff from 1820 until his death. The three completed many works while in Delessert's employ, financed by him and mostly based on his collections. These included Florae senegambiae tentamen (1831-1833, the work of Guillemin and Richard in collaboration with the collector Perrottet) and Icones selectae plantarum (1820-1845), mostly by A-P. de Candolle. Few of these botanical publications bore Delessert's name, reflecting his humble personality. Indeed, de Candolle described him in his memoirs as shy and modest. The most momentous publication produced on the collections was Lasègue's Musée botanique de M. Benjamin Delessert. An annotated list of the collections and a guide to the world's public herbaria, it was a forerunner to today's Index Herbariorum. Thanks to Lasègue, the book is not merely an enumeration of Delessert's collections but a mirror of mid-19th century taxonomic botany.

Delessert himself was so involved in helping to boost the financial situation of the French state during the Restoration years, together with his welfare projects and work in the Chamber of Deputies, that he only spent Sunday afternoons in his Musée. At his death the herbarium contained 300,000 specimens (he also had 150,000 shells in his conchology collections and a considerable number of Great Master paintings). His brothers inherited the collections with instructions to keep them accessible, which they did. The herbarium was eventually moved to Geneva, while his library was given to the Institut de France.

Sources:
F.A. Stafleu, 1970, "Benjamin Delessert and Antoine Lasègue", Taxon, 19(6): 920-929.